JP2007075130A - Ultrasonic probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe and ultrasonic diagnostic equipment capable of expanding and changing directivity of the ultrasonic probe and acquiring a diagnostic image with high resolution. <P>SOLUTION: A plurality of piezoelectric elements 1 are arranged in a direction X. Curved surfaces are formed on subject's side surfaces of acoustic matching layers 2 in a direction Y orthogonal to the arranged direction X. By changing the shapes of curved surfaces in the direction Y orthogonal to the arranged direction X, directivity can be set arbitrarily. In particular, the radius of curvature of the curved surfaces is small in the middle part to widen directivity and becomes large toward both ends. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic probe that is used to obtain diagnostic information of a subject by transmitting ultrasonic waves to a subject such as a living body.

  The ultrasonic diagnostic apparatus transmits an ultrasonic wave into a living subject such as a human or an animal, detects an echo signal reflected in the living body, displays a tomographic image of the in-vivo tissue on the monitor, and the like. Provide information necessary for diagnosis. At this time, the ultrasonic diagnostic apparatus uses an ultrasonic probe to transmit ultrasonic waves into the subject and receive echo signals from within the subject.

  FIG. 6 shows an example of a conventional ultrasonic probe. In FIG. 6, the ultrasonic probe 20 includes a plurality of piezoelectric elements 11 arranged in one direction to transmit and receive ultrasonic waves to and from a subject (not shown), and the piezoelectric elements 11. Two acoustic matching layers 12 (12a, 12b) provided on the front surface on the subject side (upper side in FIG. 6), an acoustic lens 13 provided on the subject side surface of the acoustic matching layer 12, and a piezoelectric element 11 and a back load material 14 provided on the back surface on the opposite side of the acoustic matching layer 12. Electrodes (not shown) are respectively arranged on the front surface and the back surface of the piezoelectric element 11 to transmit and receive electrical signals to and from the piezoelectric element 11.

  The piezoelectric element 11 is formed of a piezoelectric ceramic such as a PZT system, a single crystal, or a composite piezoelectric body that is a composite of the above materials and a polymer, and converts a voltage into an ultrasonic wave and transmits the ultrasonic wave into the subject. The echo reflected inside is converted into an electrical signal and received. In the illustrated example, a plurality of piezoelectric elements 11 are arranged in the X direction. Such a plurality of arrangements of the piezoelectric elements 11 can electronically scan and deflect or focus ultrasonic waves, and enable so-called electronic scanning.

  The acoustic matching layer 12 is provided for efficiently transmitting and receiving ultrasonic waves into the subject, and more specifically, plays a role of making the acoustic impedance of the piezoelectric element 11 close to the acoustic impedance of the subject stepwise. In the illustrated example, two acoustic matching layers 12a and 12b are provided, but this may be one layer or three or more layers. In the illustrated example, the acoustic matching layer 12 is integrally formed on the plurality of piezoelectric elements 11. However, the acoustic matching layer 12 is divided and arranged corresponding to each piezoelectric element 11 to widen the directivity of ultrasonic waves. A configuration is also used (for example, see Patent Document 1).

  The acoustic lens 13 plays a role of narrowing the ultrasonic beam in order to increase the resolution of the diagnostic image. In the example shown in the figure, the acoustic lens 13 is formed in a kamaboko shape that is convex in the Z direction in the figure, and the ultrasonic beam can be focused in the Y direction. The acoustic lens 13 is an optional element and is provided as necessary.

  The back load member 14 is connected to and holds the piezoelectric element 11 and further attenuates unnecessary ultrasonic waves. In the present specification, the X direction in the figure is also referred to as “(piezoelectric element) arrangement direction”, the Y direction as “(piezoelectric element) width direction”, and the Z direction as “(piezoelectric element) thickness direction”. Shall.

  In contrast to the acoustic matching layer 12 composed of a plurality of layers as described above, the prior art further discloses an acoustic matching layer 22 having a structure for continuously changing the acoustic impedance in the thickness direction as shown in FIG. (For example, refer to Patent Document 2).

  In FIG. 7, the acoustic matching layer 22 includes a first acoustic matching material 22 a having a conical or quadrangular pyramid shape having an acoustic impedance substantially equal to that of the piezoelectric element 11 and a remaining portion having an acoustic impedance substantially equal to the subject. The second acoustic matching material 22b that occupies is combined in the thickness direction.

  Specifically, the first acoustic matching material 22a is formed of a material such as glass, aluminum, ceramic, or silicon single crystal having a large acoustic impedance (acoustic impedance is close to that of the piezoelectric element 11), and the acoustic impedance is small in the gap. It is formed by filling a second acoustic matching material 22b made of epoxy resin, urethane resin, silicone rubber or the like (similar to the subject).

  The acoustic impedance can be continuously changed by arranging the lower side of FIG. 7 on the piezoelectric element 11 side and the upper side on the subject side (acoustic lens 13 side). By configuring the acoustic matching layer 22 as described above, the use frequency can be widened, and the efficiency of ultrasonic diagnosis can be increased.

On the other hand, as another ultrasonic probe, a plurality of piezoelectric elements 11 arranged in one direction are elements for transmitting and receiving ultrasonic waves, and a direction orthogonal to the arrangement direction X of the plurality of piezoelectric elements 11. The thickness of the piezoelectric element 11 of Y is thin in the vicinity of the center, and is made non-uniform so as to increase toward the end. By making the thickness of the piezoelectric element 11 non-uniform, there is a feature that the depth of focus of the ultrasonic beam is increased and a wideband frequency characteristic is obtained to improve the resolution (for example, see Patent Document 3).
JP-A-9-238399 Japanese Patent Laid-Open No. 11-89835 Japanese National Patent Publication No. 8-122310

  An electronic scanning ultrasonic diagnostic apparatus drives a piezoelectric element in an arbitrary group by giving each piezoelectric element a certain delay time, and transmits and receives ultrasonic waves from the piezoelectric element into a subject. By giving such a delay time, the ultrasonic beam is focused or deflected, and a wide visual field width or high-resolution ultrasonic image can be obtained. This is already known as a general system.

  As an ultrasound probe, it is important to obtain such a high-resolution ultrasound image from a plurality of arrayed individual piezoelectric elements that are electronically scanned to an acoustic matching layer and, if necessary, acoustics. The directivity of the ultrasonic beam emitted to the subject through the lens is excellent, that is, the directivity is wide.

  As one measure for widening the directivity, the acoustic matching layer is divided in correspondence with a plurality of piezoelectric elements arranged in one direction as shown in Patent Document 1, and acoustics between adjacent piezoelectric elements are separated. For example, a configuration in which the general coupling is reduced can be mentioned.

  However, in this configuration, the directivity is determined by the interval between a plurality of piezoelectric elements arranged in one direction, or the width and drive frequency of the piezoelectric elements, so it is difficult to further widen the directivity. . In recent years, there is a tendency that the frequency of use of the ultrasonic probe is wider, and since there are many cases where it is used at a plurality of frequencies, in order to obtain a high-resolution ultrasonic image, along with the wider bandwidth Increasing the directivity of ultrasound probes is becoming increasingly important.

  On the other hand, as a measure for changing the frequency and changing the directivity in the direction orthogonal to the arrangement direction of the plurality of piezoelectric elements, a method of changing the width of the piezoelectric elements has been proposed.

  As described above, in the present invention, the object-side surface of the acoustic matching layer is formed in a curved shape in a direction orthogonal to the arrangement direction of the plurality of piezoelectric elements, and the direction orthogonal to the arrangement direction of the plurality of piezoelectric elements. In addition, an object of the present invention is to provide an ultrasonic probe that is configured so that directivity can be arbitrarily set by changing the curved surface, thereby obtaining a high-resolution diagnostic image.

  In addition, the acoustic impedance is close to the piezoelectric element on the piezoelectric element side, and the acoustic impedance approaches the acoustic impedance of the subject as it approaches the subject side. The object-side surface of the acoustic matching layer forms a curved shape in a direction orthogonal to the arrangement direction of the plurality of piezoelectric elements, and the acoustic matching layer that enables the plurality of piezoelectric elements is formed. An object of the present invention is to provide an ultrasonic probe that can be configured to arbitrarily set directivity by changing to the curved surface in a direction orthogonal to the arrangement direction, and thereby obtain a high-resolution diagnostic image. .

  In the present invention, the directivity is improved by changing the surface curved surface shape on the subject side of the acoustic matching layer in the direction orthogonal to the arrangement direction of the plurality of piezoelectric elements arranged in one direction. The present invention relates to an ultrasonic probe characterized by being variable.

  The ultrasonic probe of the present invention includes a plurality of piezoelectric elements arranged to transmit / receive ultrasonic waves to / from at least a subject, and an acoustic matching layer provided on the subject-side front surface of the piezoelectric elements. In the ultrasonic probe composed of a pair of electrodes provided on the front surface and the back surface of the piezoelectric element, the object-side surface of the acoustic matching layer is formed in a curved shape in the direction of the plurality of piezoelectric elements. In addition, the curved surface shape changes in a direction orthogonal to the arrangement direction of the plurality of piezoelectric elements so that the directivity of the ultrasonic waves can be varied.

  With this configuration, the directivity of ultrasonic waves can be varied and widened, and the phase can be freely controlled using an array of many piezoelectric elements, and the ultrasonic beam can be narrowed down. Since the ultrasonic beam can be deflected, an ultrasonic probe that provides an ultrasonic image with high resolution can be obtained.

  In addition, the ultrasonic probe of the present invention is provided at least on a subject side front surface of a plurality of piezoelectric elements arranged in one direction in order to transmit / receive ultrasonic waves to / from a subject. In the ultrasonic probe comprising the acoustic matching layer and a pair of electrodes provided on the front surface and the back surface of the piezoelectric element, the acoustic impedance of the acoustic matching layer is a piezoelectric element at the piezoelectric element side portion. Continuously changing in the thickness direction from a value close to the object to a value close to the object in the object side portion, and the object side surface of the acoustic matching layer is curved in the direction of the plurality of piezoelectric elements The curved surface shape changes in a direction perpendicular to the arrangement direction of the plurality of piezoelectric elements.

  With this configuration, the directivity of ultrasonic waves can be varied and widened, and the phase can be freely controlled using an array of many piezoelectric elements, and the ultrasonic beam can be narrowed down. Since the ultrasonic beam can be deflected, an ultrasonic probe that provides an ultrasonic image with high resolution can be obtained.

  The ultrasonic probe of the present invention includes a plurality of piezoelectric elements arranged to transmit and receive ultrasonic waves to and from the subject, and an acoustic matching layer provided on the subject-side front surface of the piezoelectric elements. And an ultrasonic probe having a frequency variable in a direction orthogonal thereto, the object-side surface of the acoustic matching layer is formed in a curved shape in the arrangement direction of the plurality of piezoelectric elements, and the plurality The curved surface shape changes in a direction orthogonal to the arrangement direction of the piezoelectric elements.

  With this configuration, the directivity of ultrasonic waves can be varied and widened, and the phase can be freely controlled using an array of many piezoelectric elements, and the ultrasonic beam can be narrowed down. Since the ultrasonic beam can be deflected, an ultrasonic probe that provides an ultrasonic image with high resolution can be obtained.

  In the ultrasonic probe of the present invention, the curved surface shape of the object-side surface of the acoustic matching layer is composed of a combination of curved surfaces having a plurality of curvature radii, and the plurality of curvature radii change continuously or stepwise. The directivity is changed by changing the directivity.

  With this configuration, the directivity of ultrasonic waves can be varied and widened, and the phase can be freely controlled using an array of many piezoelectric elements, and the ultrasonic beam can be narrowed down. Since the ultrasonic beam can be deflected, an ultrasonic probe that provides an ultrasonic image with high resolution can be obtained.

  The ultrasonic probe of the present invention includes at least a plurality of piezoelectric elements arranged to transmit and receive ultrasonic waves to and from the subject, and an acoustic matching layer provided on the subject-side front surface of the piezoelectric elements. And an acoustic probe composed of a pair of electrodes provided on the front surface and the back surface of the piezoelectric element, the acoustic impedance of the acoustic matching layer is from a value close to that of the piezoelectric element on the piezoelectric element side portion. , Continuously changing in the thickness direction to a value close to the object at the object side portion, and the acoustic matching layer is at least 1/2 wavelength or more of the use frequency band of the ultrasonic wave generated by the piezoelectric element The object-side surface of the acoustic matching layer forms a curved surface in the arrangement direction of the plurality of piezoelectric elements, and the curved surface in a direction orthogonal to the arrangement direction of the plurality of piezoelectric elements. The shape has changed.

  With this configuration, the directivity of ultrasonic waves can be varied and widened, and the phase can be freely controlled using an array of many piezoelectric elements, and the ultrasonic beam can be narrowed down. Since the ultrasonic beam can be deflected, an ultrasonic probe that provides an ultrasonic image with high resolution can be obtained.

  Further, in the ultrasonic probe of the present invention, when the sound velocity of the subject side portion of the acoustic matching layer is Cml and the sound velocity of the subject is Cb, the curved surface with respect to the subject is concave when Cml <Cb. , Cml> Cb, the curved surface has a convex configuration.

  With this configuration, the directivity of ultrasonic waves can be varied and widened, and the phase can be freely controlled using an array of many piezoelectric elements, and the ultrasonic beam can be narrowed down. Since the ultrasonic beam can be deflected, an ultrasonic probe that provides an ultrasonic image with high resolution can be obtained.

  In the ultrasonic probe of the present invention, the curved surface shape of the object-side surface of the acoustic matching layer is composed of a combination of curved surfaces having a plurality of curvature radii, and the change in the plurality of curvature radii includes a plurality of piezoelectric radii. In a direction perpendicular to the element arrangement direction, the radius of curvature is relatively small at a position corresponding to the center of each piezoelectric element, and the radius of curvature gradually increases gradually from the center to both ends. The plurality of radii of curvature are formed to change continuously or stepwise to change the directivity.

  With this configuration, the directivity of ultrasonic waves can be varied and widened, and the phase can be freely controlled using an array of many piezoelectric elements, and the ultrasonic beam can be narrowed down. Since the ultrasonic beam can be deflected, an ultrasonic probe that provides an ultrasonic image with high resolution can be obtained.

  According to the present invention, it is possible to arbitrarily change the directivity in the arrangement direction of the piezoelectric elements of the ultrasonic probe, and it is possible to widen the frequency band and to obtain a high-resolution diagnostic image. Tentacles can be provided.

  Hereinafter, an ultrasonic probe according to a first embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a partial schematic perspective view of an ultrasonic probe 10 according to the first embodiment of the present invention, and FIG. 2 is a partially enlarged view of a portion A shown in FIG.

  1 and 2, an ultrasonic probe 10 is basically the same as that according to the prior art shown in FIG. 7, and includes a plurality of piezoelectric elements 1 arranged in one direction (X direction) and each piezoelectric element. The acoustic matching layer 2 disposed on the front surface in the thickness direction (Z direction) corresponding to 1 on the subject side (upper side in the figure), and the thickness opposite to the acoustic matching layer 2 with respect to the piezoelectric element 1 It is comprised from the back surface load material 3 arrange | positioned at a direction (Z direction) back surface (lower side of a figure). The functions of these components are the same as those described in the prior art.

  A ground electrode 4 is provided on the front surface of the piezoelectric element 1 in the thickness direction Z, and a signal electrode 5 is provided on the back surface. Both electrodes 4 and 5 are formed on the front surface and the back surface of the piezoelectric element 1 by vapor deposition of gold or silver, sputtering, or baking of silver, respectively.

  Both electrodes 4 and 5 are electrically connected to an ultrasonic diagnostic apparatus (not shown) via a cable via an electric terminal 6, and apply a regular pulse voltage generated by the ultrasonic diagnostic apparatus to the piezoelectric element 1. The echo receiving wave converted into an electric signal by the piezoelectric element 1 is transmitted to the ultrasonic diagnostic apparatus body.

  Further, in the illustrated example, the acoustic matching layer 2 is individually divided corresponding to each piezoelectric element 1, and the divided grooves are made of silicone rubber, urethane rubber, or the like that has a small acoustic coupling. Such a material is filled. As described above, by dividing the acoustic matching layer 2 so as to correspond to each piezoelectric element 1, an effect of widening the directivity of ultrasonic waves can be obtained.

  3 shows the surface shape of the acoustic matching layer 2 on the object side 7 (see FIG. 2) with respect to the Y direction (width direction) perpendicular to the arrangement direction X of the plurality of piezoelectric elements 1 shown in FIG. Is a diagram schematically representing a change in the radius of curvature having a curved surface in the arrangement direction X of the plurality of piezoelectric elements 1 and the change in the directionality corresponding thereto.

  In the so-called electronic scanning type ultrasonic probe 10 in which the plurality of piezoelectric elements 1 are arranged, the directivity in the arrangement direction X of the piezoelectric elements 1 arranged in one direction can be increased, or any directivity can be obtained. Whether it can be provided is an important point for improving the resolution of the ultrasonic image.

  In the present embodiment, as shown in FIG. 2, the surface 2s on the subject side of the acoustic matching layer 2 is formed into a curved surface along the arrangement direction X of the piezoelectric elements 1, and the directivity is arbitrarily set with respect to the Y direction. It is supposed to change. That is, the surface 2 s of the acoustic matching layer 2 has a curved surface, so that the ultrasonic beam can be diffused in the arrangement direction X of the piezoelectric elements 1.

  Specifically, by utilizing the difference between the sound velocity Cml of the acoustic matching layer 2 and the sound velocity Cb of the subject, the ultrasonic wave is refracted by forming the surface shape into a concave or convex curved surface. It is intended to diffuse and change the directivity.

  In FIG. 3, the horizontal axis represents the Y direction, and the vertical axis represents the magnitude of the curvature radius of the surface 2 s of the acoustic matching layer 2 and the corresponding directivity width. In FIG. 3, when the radius of curvature of the acoustic matching layer 2 is decreased at the center in the Y direction and gradually increased gradually toward both ends, the directivity is the largest in the center in the Y direction. It is wide and indicates that it gradually narrows as it goes to both ends.

  For example, when an epoxy resin is used as the acoustic matching layer material constituting the acoustic matching layer 2, the sound velocity Cml is about 2.5 km / second. On the other hand, if the subject 7 is a living body, for example, the sound speed Cb of the subject is about 1.53 km / second, and the relationship of Cml> Cb is established between the two.

  In this case, as shown in FIGS. 1 and 2, if the shape of the surface of the acoustic matching layer 2 is convex with respect to the subject 7, the ultrasonic wave is diffused, so the directivity can be widened. . By changing the curvature radius of the convex surface with respect to the Y direction, it becomes possible to obtain directivity corresponding to each curvature radius. The convex surface at this time can be formed into, for example, a convex shape having a single radius of curvature.

  Further, when the relationship between the sound speeds is opposite, if the subject 7 is also a living body, the relationship Cml <Cb is established. In this case, if the shape of the surface of the acoustic matching layer 2 is concave, the ultrasonic wave is diffused, so that the directivity can be widened. The concave surface at this time can be formed into, for example, a concave shape having a single radius of curvature.

  In this way, the curvature radius of the surface 2s of the acoustic matching layer is reduced at the center portion in the Y direction, and the curvature radius is increased substantially continuously toward the both end portions. The directivity (X direction) of the element 1 has a directivity characteristic that the directivity is the widest at the center in the Y direction (width direction) and gradually decreases toward both ends.

  On the other hand, the ultrasonic beam by electronic delay control in the arrangement direction X of the piezoelectric elements 1 can be narrowed at an arbitrary distance (depth). In a region that is far (deep) from the piezoelectric element 1, the ultrasonic beam can be narrowed even if the directivity is not so wide. Since the directivity is greatly affected at a short distance and the degree of diaphragming of the ultrasonic beam is changed, a characteristic having a wide directivity is desired.

  In this embodiment, since the directivity is the widest in the vicinity of the central portion, the greatest contribution is made when the ultrasonic beam is narrowed by electronic control to a close distance, and the contribution becomes smaller toward both ends. Therefore, in the Y direction of the piezoelectric element 1, since the ultrasonic beam is controlled with a small opening near the central region, an ultrasonic image with high resolution can be obtained in the short-distance region, and even in a long distance. Since all the widths in the Y direction can be used effectively, an ultrasonic image with high resolution can be obtained.

  The curved surface shape of the surface 2s of the acoustic matching layer 2 is a curved surface having a constant radius of curvature with respect to the arrangement direction X of the piezoelectric elements 1, but is not limited thereto, and has, for example, a plurality of curvature radii. It may be another shape that can change the directivity by changing the shape of the curved surface, trapezoid, or polygon.

  The curved surface shape of the surface 2s of the acoustic matching layer 2 has been described in the case where the radius of curvature is continuously varied with respect to the Y direction. The same effect can be obtained even when changing.

  In this way, by adopting a configuration in which the curved surface shape of the surface 2s of the acoustic matching layer 2 is changed in the Y direction, an ultrasonic beam is electronically used by using a plurality of piezoelectric elements 1 in the central portion of the Y direction with a wide directivity. Can be deflected or converged.

  This is particularly effective when a diagnosis is performed in a region where the diagnosis depth is shallow using a high frequency. On the other hand, a region having a deeper diagnosis depth is mainly at both ends in the Y direction, so that directivity is not necessary so much and ultrasonic waves can be effectively used up to both ends.

  By changing the curved surface shape of the acoustic matching layer 2 in the Y direction (width direction), it becomes possible to change the directivity in the Y direction of the piezoelectric element 1. Apparently, the Y direction of the ultrasonic probe 10 is changed. It becomes close to the state where the opening width is variable. For this reason, it becomes possible to improve the resolution of the diagnostic image from a shallow region to a deep region.

  In the example shown in FIGS. 1 and 2, the acoustic matching layer 2 is divided into a plurality of parts corresponding to each piezoelectric element 1, and both electrode surfaces of the divided piezoelectric element 1, particularly the signal electrode 6, are signal electric. Connected to a terminal (not shown), each can send and receive ultrasonic waves independently.

  In order to change the directivity, it is preferable that the acoustic matching layer 2 is divided in correspondence with each piezoelectric element 1 as described above. However, the acoustic matching layer 2 is not divided and the acoustic matching layer 2 is not divided. Even when the surface shape on the subject 7 side is configured such that the curved surface shape is variable in the Y direction in accordance with the arrangement interval of the piezoelectric elements 1, the effects specific to the present invention can be obtained.

(Second Embodiment)
Next, an ultrasonic probe according to a second embodiment of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the part similar to the ultrasound probe of 1st Embodiment, and detailed description is abbreviate | omitted.

  FIG. 4 shows a partial schematic perspective view of the ultrasonic probe 10 according to the second embodiment. In FIG. 4, an ultrasonic probe 10 is basically the same as that according to the prior art shown in FIG. 6, and includes a plurality of piezoelectric elements 1 and a subject 7 side corresponding to each piezoelectric element 1 (shown in the figure). The acoustic matching layer 2 disposed on the front surface in the thickness direction Z (upper) and the rear surface disposed on the rear surface (lower side in the figure) in the thickness direction Z opposite to the acoustic matching layer 2 with respect to the piezoelectric element 1. It is comprised from the load material 3. FIG. The functions of these components are the same as those described in the prior art.

  A ground electrode 4 is provided on the front surface of the piezoelectric element 1 in the thickness direction Z, and a signal electrode 5 is provided on the back surface. Both electrodes 4 and 5 are formed on the front surface and the back surface of the piezoelectric element 1 by vapor deposition of gold or silver, sputtering, or baking of silver, respectively.

  Both electrodes 4 and 5 are electrically connected to an ultrasonic diagnostic apparatus (not shown) via a cable, and a regular pulse voltage generated by the ultrasonic diagnostic apparatus is applied to the piezoelectric element 1. The echo reception wave converted into is transmitted to the ultrasonic diagnostic apparatus body.

  Further, in the illustrated example, the acoustic matching layer 2 is individually divided corresponding to each piezoelectric element 1, and the divided grooves are made of silicone rubber, urethane rubber, or the like that has a small acoustic coupling. Such a material is filled. As described above, the acoustic matching layer 2 is divided and configured so as to correspond to each piezoelectric element 1 as described above, thereby obtaining an effect of widening the directivity of ultrasonic waves.

The acoustic matching layer 2 used in the ultrasonic probe 10 according to the present embodiment has a characteristic that acoustic impedance continuously changes in the thickness direction.
That is, the portion of the acoustic matching layer 2 located on the piezoelectric element 1 side (or the ground electrode 6 side) has an acoustic impedance close to that of the piezoelectric element 1. Further, the portion of the acoustic matching layer 2 located on the subject 7 side has an acoustic impedance close to that of the subject 7.

  The acoustic impedance is continuously inclined in the thickness direction between the portion of the acoustic matching layer 2 located on the piezoelectric element 1 side and the portion located on the subject 7 side. More specifically, the acoustic impedance on the ground electrode 4 side of the acoustic matching layer 2 is about 30 megarail (when the piezoelectric element 1 is a piezoelectric ceramic such as a PZT system), and the acoustic impedance on the subject 7 side is about 1. It is about 5 megarails, and the acoustic impedance changes continuously during that time.

  Such a continuous change in acoustic impedance is caused by, for example, the acoustic matching layer 2 having a conical or quadrangular pyramid having an acoustic impedance substantially equal to that of the piezoelectric element 1, as shown in the prior art section with reference to FIG. The first acoustic matching material 22a having a polygonal pyramid shape and the like, and the second acoustic matching material 22b occupying the remaining portion having substantially the same acoustic impedance as the subject 7 are combined in the thickness direction Z. Can be obtained.

  In addition to this method, for example, a resin with an acoustic impedance close to the subject is filled with a powder having a high specific gravity (high acoustic impedance) such as tungsten powder, and the degree of powder filling in the resin is increased. A continuous change in acoustic impedance can also be obtained by other alternative methods such as tilting in the direction.

  By using the acoustic matching layer 2 in which the acoustic impedance is continuously inclined as described above, the frequency band can be widened. In addition, when the acoustic matching layer 2 that continuously changes the acoustic impedance as described above is used, the signal intensity distribution does not depend on the frequency, and the thickness of the acoustic matching layer 2 is reduced to about the use frequency band. If the wavelength is ½ wavelength or more, the thickness and the frequency characteristic are not so much.

  In the so-called electronic scanning type ultrasonic probe in which a plurality of piezoelectric elements are arranged in one direction, it is important to improve the resolution of the ultrasonic image whether the directivity can be widened or changed arbitrarily. It is a point. In the present embodiment, attention is paid to the fact that the thickness does not affect the frequency characteristics in the acoustic matching layer 2 in which the acoustic impedance is continuously tilted. The surface 2s is formed into a curved surface along the arrangement direction of the piezoelectric elements 1 to increase the directivity, and the curved surface shape is changed with respect to the Y direction to change the directivity. .

That is, the surface shape of the acoustic matching layer 2 has a curved surface, and by changing the curved surface shape, the diffusion of the ultrasonic beam in the arrangement direction of the piezoelectric elements 1 can be changed in the Y direction.
Specifically, by utilizing the difference between the sound velocity Cml near the surface of the acoustic matching layer 2 and the sound velocity Cb of the subject, the ultrasonic wave is formed by forming the surface shape into a concave or convex curved surface. It is refracted and diffused to widen and change the directivity.

  For example, when silicone rubber is used as one acoustic matching material (reference numeral 22b in FIG. 7) constituting the acoustic matching layer 2, the sound velocity Cml on the subject side of the acoustic matching layer 2 is about 100 km / sec. On the other hand, if the subject 7 is a living body, for example, the sound speed Cb of the subject is about 1.53 km / second, and the relationship of Cml <Cb is established between the two.

  In this case, if the shape of the surface 2 s of the acoustic matching layer 2 is concave with respect to the subject 7, the directivity can be widened because the ultrasonic waves are diffused. By changing the curvature radius of the concave surface with respect to the Y direction, directivity corresponding to each curvature radius can be obtained. The concave surface at this time can be, for example, a concave shape having a single radius of curvature.

  Also, the relationship between the sound speeds is opposite to this, that is, when a material mainly composed of epoxy resin or the like is used as the sound matching material constituting the sound matching layer 2, the sound speed Cml on the subject side of the sound matching layer 2 is about 2 to 2.6 km / sec. If the subject is a living body, the relationship of Cml> Cb is established.

  In this case, if the shape of the surface 2s on the subject 7 side of the acoustic matching layer 2 is a convex surface as shown in FIG. 3, the ultrasonic wave is diffused, so that the directivity can be widened. By changing the curvature radius of the convex surface substantially continuously in the Y direction, it becomes possible to obtain directivity corresponding to each curvature radius. The convex surface at this time can be, for example, a convex shape having a single radius of curvature.

  In this way, the surface 2s on the subject 7 side of the acoustic matching layer 2 is formed into a curved surface according to the relationship with the sound speed of the subject, and the curved surface shape is changed with respect to the Y direction, thereby providing arbitrary directivity. Can be made. In the case of such a configuration, the surface of the acoustic matching layer 2 becomes a curved surface with respect to the arrangement direction X of the piezoelectric elements 1 and the thickness thereof changes.

  This means that in the case of an acoustic matching layer composed of a single layer or a plurality of layers having a conventional configuration, the frequency characteristics fluctuate due to the change in thickness, and thus desired characteristics cannot be obtained. ing. In other words, if the conventional acoustic matching layer is used, either frequency characteristics or directivity must be sacrificed.

  On the other hand, when the acoustic matching layer 2 in which the acoustic impedance according to the present embodiment is continuously inclined is used, if the thickness of the acoustic matching layer 2 is set to ½ wavelength or more of the used frequency band, Even if the surface is curved and its thickness changes, there is no effect on the frequency characteristics, and in addition to widening the frequency band by continuous change in acoustic impedance, widen directivity Can be obtained.

  The curved surface shape of the surface 2s of the acoustic matching layer 2 is a curved surface having a constant radius of curvature with respect to the arrangement direction of the piezoelectric elements 1, but is not limited thereto, and is, for example, a curved surface having a plurality of curvature radii. Alternatively, the trapezoidal shape or the polygonal shape may be changed so that the directivity can be varied.

  In addition, the curved surface shape of the surface of the acoustic matching layer 2 has been described in the case where the radius of curvature is continuously variable with respect to the Y direction. Even if it changes, the same effect is acquired.

  In this way, by adopting a configuration in which the curved surface shape of the surface of the acoustic matching layer 2 is changed in the Y direction, the ultrasonic beam is electronically deflected using a plurality of piezoelectric elements 1 in the central portion of the Y direction with a wide directivity. Or it can be made to converge.

  This is particularly effective when making a diagnosis in a region where the diagnosis depth is shallow using a high frequency. On the other hand, a region having a deeper diagnosis depth is mainly at both ends in the Y direction, so that directivity is not necessary so much and ultrasonic waves can be effectively used up to the end.

  By changing the curved surface shape of the acoustic matching layer 2 in the Y direction, the directivity can be changed in the width direction of the piezoelectric element 1, and apparently the opening width of the ultrasonic probe 10 is variable. Close to the state. For this reason, it becomes possible to improve the resolution of the diagnostic image from a shallow region to a deep region.

  In the example shown in FIG. 3, the acoustic matching layer 2 is divided into a plurality of parts corresponding to each piezoelectric element 1, and both electrode surfaces of the divided piezoelectric element 1, particularly the signal electrode 5, are signal electrical terminals ( Are connected to each other (not shown) so that each can independently transmit and receive ultrasonic waves.

  In order to make the directivity variable, it is preferable that the acoustic matching layer 2 is divided according to each piezoelectric element 1 as described above. However, the acoustic matching layer 2 is not divided, but the acoustic matching layer 2 is not divided. Even in the case where the surface shape on the subject side of the layer 2 is adapted to the arrangement interval of the piezoelectric elements 1 and the curved surface shape is variable in the Y direction, the effect specific to the present application can be obtained.

(Third embodiment)
Next, an ultrasonic probe according to a third embodiment of the present invention will be described with reference to the drawings. FIG. 5 shows a partial schematic perspective view of the ultrasonic probe 10 according to the present embodiment.

  In FIG. 5, an ultrasonic probe 10 is basically the same as that according to the prior art shown in FIG. 6, and a plurality of piezoelectric elements 1 and a subject 7 side corresponding to each piezoelectric element 1 (shown in the figure). The acoustic matching layer 2 disposed on the front surface in the thickness direction Z (upper) and the rear surface (lower side in the figure) in the thickness direction Z opposite to the acoustic matching layer 2 with respect to the piezoelectric element 1 It is comprised from the back surface load material 3. The functions of these components are the same as those described in the prior art.

  Here, the thickness in the direction Y orthogonal to the arrangement direction X of the piezoelectric elements 1 is made non-uniform so as to become thinner toward the end in the Y direction near the center, and has a curved shape. By making the thickness of the piezoelectric element 1 non-uniform, the depth of focus of the ultrasonic beam can be increased, and a wideband frequency characteristic can be obtained to improve the resolution.

  Near the center of the piezoelectric element 1 in the Y direction, since the thickness is small, ultrasonic waves with high frequency components are transmitted and received, and the thickness increases toward both ends, so that ultrasonic waves with low frequency components are transmitted and received. On the other hand, the width in the arrangement direction X of the piezoelectric elements 1 is the same as the direction Y orthogonal to the arrangement direction X of the piezoelectric elements 1.

  In the orthogonal direction Y, the piezoelectric element 1 has a high frequency because the thickness of the central part is thin, and becomes thicker toward the both ends. The directivity of the sound wave is narrower at the higher frequency at the center and wider at the lower frequency at both ends.

  In the arrangement direction X of the piezoelectric elements 1, the plurality of piezoelectric elements 1 are electronically delayed and phase controlled to narrow down or deflect the ultrasonic beam. Desirable for obtaining ultrasound images.

  However, in this configuration, since the central portion of the piezoelectric element 1 has a narrow directivity, the range in which phase control can be performed becomes narrow, and as a result, it is difficult to obtain a high-resolution ultrasonic image. In contrast, in the present embodiment, the shape of the object-side surface of the acoustic matching layer 2 can be eliminated by changing the shape so as to be a curved surface in the Y direction.

  That is, the portion located in the central portion in the Y direction has a high frequency component because the thickness of the piezoelectric element 1 is thin, and the piezoelectric element 1 becomes thicker as it goes to both ends, and therefore has a low frequency component. Corresponding to this change in frequency, the surface of the object side of the acoustic matching layer 2 is curved to change the directivity, and the curved surface (curvature radius) has a high frequency component at the center. Let's make the directivity variable according to the frequency of each position by increasing the directivity gradually and gradually increasing the radius of curvature almost continuously as going to both ends. Is possible.

  Thereby, the problem that the directivity in the center part which has a high frequency component like the past becomes narrow can be solved. Therefore, the directivity of the center portion having a high frequency is made the same as the directivity of both end portions having a low frequency component, and the directivity of the surface 2s of the acoustic matching layer 2 is arbitrarily selected. Is possible.

  The surface of the acoustic matching layer 2 on the subject side has a curved surface that is a convex curved surface or a concave curved surface depending on the ratio of the acoustic velocity of the acoustic matching layer 2 and the subject, as described in the first and second embodiments. You can choose what to do.

  In addition, when a material that continuously changes the acoustic impedance is used for the acoustic matching layer 2, if the thickness of the acoustic matching layer 2 is about ½ wavelength or more of the operating frequency band, the thickness and frequency characteristics Therefore, if the thickness is set to be 1/2 wavelength or lower of the low frequency at both ends, the thickness may be uniform, and there is an advantage that it is easy to change the curved surface shape in the Y direction.

  The curved surface shape of the surface 2s of the acoustic matching layer 2 is a curved surface having a constant radius of curvature with respect to the arrangement direction X of the piezoelectric elements 1, but is not limited thereto, and has, for example, a plurality of curvature radii. It may be another shape that can change the directivity by changing the shape of the curved surface, trapezoid, or polygon.

  In addition, the curved surface shape of the surface of the acoustic matching layer 2 has been described in the case where the radius of curvature is continuously variable with respect to the Y direction. Even if it changes, the same effect is acquired.

  Thus, by adopting a configuration in which the curved surface shape of the surface of the acoustic matching layer 2 is changed in the Y direction, an ultrasonic beam is electronically used by using a plurality of piezoelectric elements 1 in the central portion of the Y direction having a wide directivity. It is possible to deflect or converge.

  This is particularly effective when making a diagnosis in a region where the diagnosis depth is shallow using a high frequency. On the other hand, the end portion in the Y direction is mainly a region having a deeper diagnosis depth, and directivity is not so much required, so that ultrasonic waves can be effectively used up to the end portion.

  By changing the curved surface shape of the acoustic matching layer 2 in the width direction Y, it becomes possible to change the directivity in the width direction Y of the piezoelectric element 1, and apparently the opening width of the ultrasonic probe 10 can be varied. It becomes close to the state. For this reason, it becomes possible to improve the resolution of the diagnostic image from a shallow region to a deep region.

  In the example shown in FIG. 5, the acoustic matching layer 2 is divided and arranged in a plurality corresponding to each piezoelectric element 1, and both electrode surfaces of the divided piezoelectric element 1, particularly the signal electrode 5, are signal electrical terminals ( Connected to each other (not shown) so that each can transmit and receive ultrasonic waves independently.

  In order to change the directivity, the acoustic matching layer 2 is preferably divided in correspondence with each piezoelectric element 1 as described above. However, the acoustic matching layer 2 is not divided, but the acoustic matching layer is not provided. Even in the case where the curved surface shape is variable in the Y direction by matching the surface shape of the object 2 on the subject side with the arrangement interval of the piezoelectric elements 1, the effect specific to the present invention can be obtained.

  The ultrasonic probe according to the present invention can be used in various medical fields for performing ultrasonic diagnosis of a subject such as a human body and in industrial fields for the purpose of internal flaw detection of materials and structures.

1 is a schematic perspective view showing an ultrasonic probe according to a first embodiment of the present invention. FIG. 2 is a partially enlarged side view showing one aspect of the ultrasonic probe shown in FIG. 1. It is a qualitative schematic diagram showing the relationship between the radius of curvature of the acoustic matching layer surface and directivity. It is a schematic perspective view which shows the ultrasonic probe of 2nd Embodiment which concerns on this invention. It is a schematic perspective view which shows the ultrasonic probe of 3rd Embodiment which concerns on this invention. It is a schematic perspective view which shows the structure of the ultrasonic probe by a prior art. It is a schematic perspective view which shows the structure of the acoustic matching layer which the acoustic impedance by a prior art inclines continuously.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2 Acoustic matching layer 3 Back surface load material 4 Ground electrode 5 Signal electrode 6 Electrical terminal 7 Subject 10 Ultrasonic probe 11 Piezoelectric element 12 Acoustic matching layer 13 Acoustic lens 14 Back surface load material 20 Ultrasonic probe 22 acoustic matching layer 22a first acoustic matching material 22b second acoustic matching material

Claims (7)

A plurality of piezoelectric elements arranged to transmit and receive ultrasonic waves to and from the subject;
An acoustic matching layer provided on the subject-side front surface of the plurality of piezoelectric elements;
In the ultrasonic probe comprising a pair of electrodes provided on the front surface and the back surface of the plurality of piezoelectric elements,
The object-side surface of the acoustic matching layer is formed in a curved shape on the plurality of piezoelectric element sides,
The ultrasonic probe, wherein the curved surface is curved in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements. A plurality of piezoelectric elements arranged to transmit and receive ultrasonic waves to and from the subject;
An acoustic matching layer provided on the subject-side front surface of the plurality of piezoelectric elements;
In the ultrasonic probe comprising a pair of electrodes provided on the front surface and the back surface of the plurality of piezoelectric elements,
The acoustic impedance of the acoustic matching layer continuously changes in the thickness direction from a value close to the piezoelectric element in the plurality of piezoelectric element side portions to a value close to the subject in the subject side portion,
The object-side surface of the acoustic matching layer is formed in a curved shape on the plurality of piezoelectric element sides,
The ultrasonic probe, wherein the curved surface is curved in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements. A plurality of piezoelectric elements arranged to transmit and receive ultrasonic waves to and from the subject;
An acoustic matching layer provided on the subject-side front surface of the piezoelectric element;
In an ultrasonic probe having a configuration in which the frequency is variable in a direction perpendicular to the direction,
The object-side surface of the acoustic matching layer is formed in a curved shape on the plurality of piezoelectric element sides,
The ultrasonic probe, wherein the curved surface is curved in a direction orthogonal to an arrangement direction of the plurality of piezoelectric elements. The curved surface shape on the subject side surface of the acoustic matching layer is composed of a combination of curved surfaces having a plurality of curvature radii,
4. The ultrasonic probe according to claim 1, wherein the plurality of radii of curvature change continuously or stepwise.   The ultrasonic probe according to claim 2, wherein the acoustic matching layer has a thickness of at least a half wavelength or more of a use frequency band in an ultrasonic wave generated by the piezoelectric element.   When the sound velocity of the subject side portion of the acoustic matching layer is Cml and the sound velocity of the subject is Cb, the curved surface with respect to the subject is concave when Cml <Cb, and the curved surface when Cml> Cb. The ultrasonic probe according to any one of claims 1 to 4, which has a convex shape.   The change in the plurality of curvature radii is such that, in a direction orthogonal to the arrangement direction of the plurality of piezoelectric elements, the curvature radius is relatively small at a position corresponding to the center of each piezoelectric element, and from the center to both ends. The ultrasonic probe according to claim 4, wherein the curvature radius is formed so that the radius of curvature becomes relatively gradually larger as it advances.

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